modules/world: derive the Actor2D from the base actor

gamecore/modules/world/actors/actor2D.lua

@@ -23,16 +23,16 @@
 ]]
 
 local cwd   = (...):gsub('%.actor2D$', '') .. "."
+local BaseActor = require(cwd .. "baseactor")
+local Actor2D = BaseActor:extend()
 
-local Actor2D = Object:extend()
 local Timer   = require(cwd .. "utils.timer")
 
 -- INIT FUNCTIONS
 -- Initialise the actor and its base functions
 
 function Actor2D:new(world, type, x, y, w, h, isSolid)
-  self.type   = type or ""
-
+  Actor2D.super.new(self, world, type)
   self:setManagers(world)
   self:initPhysics(x, y, w, h, isSolid)